This invention relates generally to apparatus for aerating and maintaining an ice free surface area in a body of water. More specifically, it relates to apparatus for aerating and maintaining an ice free surface area in a pond or lake.
It is well known to those skilled in this particular field that fish require oxygen to live. Conservation authorities have determined that most fish can stay alive in as little as three parts of air per million parts of water. This is the absolute minimum merely to keep them alive. To keep them healthy and growing, higher levels of oxygen are necessary.
Nature provides oxygen in two ways, absorption from the air, and from underwater plant life. In the summer, when the surface of a pond or lake is open to the air, wind and wave action stirs the surface causing air to be absorbed and distributed below the surface. Plants living under water give off oxygen through photosynthesis, using energy from the sun.
Large bodies of water such as the oceans, seas, large natural lakes and rivers generally maintain adequate oxygen content for survival and growth of fish. However, in relatively smaller bodies of water such as artificial ponds and small lakes where fish are raised for sale or recreation, there is a definite danger of oxygen depletion to the point where fish will not survive through the winter if a solid layer of ice prevents absorption of atmospheric air. The problem is worsened when snow accumulates on the ice and prevents sunlight from filtering through and keeping the oxygen-generating underwater plants alive.
The result, following the spring thaw, is hundreds or thousands of dead fish floating to the surface and washing ashore representing the loss of hundreds or thousands of dollars, and five years or more in bringing a pond or lake to peak production.
One common way of maintaining the life-supporting oxygen content of a stocked pond or lake through the winter months is to aerate it through one or more air diffusion units submerged beneath the surface and connected through an air line such as a pipe or hose to an air compressor on shore. This works fine as long as the air compressor runs continuously and keeps the air line filled with air all the way to the submerged air diffusion unit. However, air compressors are among the least efficient users of energy, and it is costly to run them all the time unnecessarily, especially at the beginning and end of the icing season when adequate aeration can be maintained running them only part time. It is customary, therefore, to turn them on and off manually, or by pre-set automatic timers, during those parts of the year when less than 24-hour-per-day operation is needed.
This poses a serious problem. In conventional pond aerating systems, prior to the present invention, water backed up all the way to the surface of the pond at the point where the air line entered the water, when the compressor was shut off. Due to the peculiar density/temperature properties of water, higher density, warmer water remains liquid just a few feet below the surface, while the lower density, colder water rises to the surface and forms ice. If the water in the air line is allowed to flow back into the ice area, for any length of time, it, too, will freeze, blocking any further flow of air. At this time, the system is out of operation, unless the plug of ice can be found and removed from the air line.
Such ice blockage of the air line can occur even when the compressor is set for full 24 hour, continuous operation, as for example when the power fails. As a matter of actual fact, such power failures are far more common in remote or rural areas where fish ponds are maintained, than in heavily populated urban areas. This situation is accordingly in need of improvement.